The rotating disc of the disc-screw microinjection molding machine determines its plasticizing performance, but the structural design of the rotating disc often depends on designer's experience and lacks theoretical basis. In this study, the multiphysics coupling finite element model of the plasticizing unit with a rotating disc was established, and the rotating discs with different structural parameters were simulated under the same process parameters, aiming at plasticizing performance to obtain the optimal structure of the rotating disc. Furthermore, the new rotating disc optimized for rapid processing by metal 3D printing was used for experimental verification. Polypropylene (PP), polylactic acid (PLA) and high-density polyethylene (HDPE) were respectively used for injection mass repeatability experiments, tensile experiments and thermodynamic properties experiments. The experimental results were analyzed to verify that the new rotating disc had better plasticizing properties. The results show that the multiphysical field simulation can provide quantitative analysis basis for the optimal design of the rotating disc structure of the disc-screw microinjection molding machine, and the metal 3D printing can provide technical means for the rapid development of the rotating disc.